Forming foundry cores



Patented Jan. 22, 1952 Robert S. Wolf, Chicago, Ill.

No Drawing. Application July 8, 1947, Serial No. 759,719

9 Claims. 1

This invention relates to the formation of foundry cores and is animprovement upon the methods and products described in my co-pendingapplication, Serial No. 733,921, filed April 2, 1947, now abandoned.

The common adhesive heretofore used to impregnate core sand is a form ofoil. It has the disadvantage of causing a disagreeable irritating smokeand odor when the casting is poured. It also generates gases which causedefects in the castings. Likewise the cores when baked have solid crustswhich can be broken only with difficulty.

As set forth in my aforesaid application, I have found that by usingsoluble cellulose derivatives and particularly methyl cellulose and itsderivatives such as carboxy methyl cellulose and its salts, the defectsof the oil from the adhesives may be eliminated.

The new adhesives are introduced into the sand in any suitable manner,normally by dissolving at least a portion of the adhesive in a solvent,such as water, and then mixing the sand and the adhesive.

I have found that an improved core may be produced if an unbaked coreproduced by the process of my aforesaid application is exposed, in atleast its outer section, to an atmosphere consisting substantially of asolvent for the adhesive and this exposure is continued longenoughsubcore in which the exterior is substantially harder and tougherthan the interior.

This process also has the advantage that it permits the use of morehighly viscous adhesive solutions, which may not otherwise wet and bindthe sand particles. It thus permits the use of higher solid contentsolutions of the adhesive.

The preferred method of creating an atmosphere of the solvent is toplace cores within an enclosed chamber such as a steam kettle whereinvapors of the solvent may be generated, pref erably undersuper-atmospheric pressure. Usually one or two pounds atmosphericpressure is necessary and a treatment of only five to ten minutes isadequate.

The core may be placed within the kettle on the usual plates but in suchcase it is preferred to pre-heat the kettle and plates to approximately212 F. in order to avoid condensation thereon.

The atmosphere of solvent may be generated within the core as by the useof high frequency current, but under present conditions this is noteconomical.

It is also possible to employ a steam tunnel or direct jets of steam,saturated or superheated.

Where the solvent is other than water, it is usually desirable to use anenclosed system so that the solvent may be recovered.

The preferred adhesive. is a cellulose derivative able to withstand 212F. without becoming insoluble. Sodium carboxy methyl cellulose isparticularly suitable. The present invention is not necessarily limitedto such cellulose derivatives but is applicable to other solubleadhesives.

The foregoing detailed description is given for clearness ofunderstanding only, and no unnecessary limitations should be understoodtherefrom, for some modifications will be obvious to those skilled inthe art.

I claim:

1. The method of forming foundry cores which comprises treating foundrysand with a soluble adhesive, forming the so treated sand into acoherent core, and then exposing the outer portions of the core, priorto baking, to an atmosphere containing solvent in proportion and at atemperature to condense upon the adhesive upon the sand, and continuingthe exposure until the flowability of the adhesive in the exposedportions of the core has substantially increased.

2. The method as set forth in claim 1, in which the adhesive is watersoluble and the atmosphere is one consisting essentially of steam.

3. The method as set forth in claim 1, in which the adhesive comprises acellulose derivative.

4. The method as set forth in claim 1, in which the adhesive comprises asalt of carboxy methyl cellulose.

5. The method as set forth in claim 1 in which the adhesive comprises awater soluble compound and the atmosphere consists substantially ofsteam.

6. The methods as set forth in claim 5 in which the atmosphere comprisessteam under super-atmospheric pressure.

7. A method as set forth in claim 1 in which the cores are preheated toa non baking temperature substantially above atmospheric prior toexposure to the solvent atmosphere.

8. The method of forming foundry cores which comprises treating foundrysand with a soluble adhesive, forming the so treated sand into acoherent core, and then exposing the outer portions of the core, priorto baking to an atmosphere con- 3 4 taining solvent in proportion and ata temperature to condense upon the adhesive upon the UNITED STATESPATENTS sand, and continuing the exposure until the fiow- Number m Dateability of the adhesive in the exposed portions 7 Lane June 10 7 of thecore has substantially increased, and then 5 9 355 Bean 25 1945 ba tCore- 2,398,047 Schmidt Apr. 9, 1946 9. The method as set forth in claim8, in which 2,435,353 Whitehead 10, 1948 the adhesive is a salt ofcarboxy methyl cellulose.

- ROBERT 5. W013 OTHER REFERENCES 10 "New Binders Improve CorePerformance," REFERENCES CITED by Gebharclt, article in The Iron Age,December The following references are of record in the 26, 1946- Pagesfile of this patent:

